It shouldn't have any effect. DT-INTS saves the system variables when entering the ISR so even if an interrupt happens in between the multiplication and the division AND the ISR happens to use the same system variables (R0 and R2 IIRC) holding the 32 bit result from the multiplication no harm is done since the content of those variables are restored by DT-INTS when exiting the ISR.

/Henrik.